Reagents are added to soils contaminated with halogenated organics. The
dehalogenation process is achieved by either the replacement of the halogen
molecules or the decomposition and partial volatilization of the contaminants.

Contaminated soil is screened, processed with a crusher and pug mill, and
mixed with reagents. The mixture is heated in a reactor. The dehalogenation process is
achieved by either the replacement of the halogen molecules or the decomposition and
partial volatilization of the contaminants.

Base-catalyzed
Decomposition (BCD)

Base-catalyzed decomposition (BCD) process was developed by EPA's Risk Reduction
Engineering Laboratory (RREL), in cooperation with the Naval Facilities Engineering
Services Center (NFESC) to remediate soils and sediments contaminated with chlorinated
organic compounds, especially PCBs, dioxins, and furans. Contaminated soil is screened,
processed with a crusher and pug mill, and mixed with sodium bicarbonate. The mixture is
heated to above 330 °C (630°F) in a reactor to partially decompose and volatilize the
contaminants. The volatilized contaminants are captured, condensed, and treated
separately.

Glycolate/Alkaline Polyethylene Glycol (APEG)

Glycolate is a full-scale technology in which an alkaline polyethylene glycol (APEG)
reagent is used. Potassium polyethylene glycol (KPEG) is the most common APEG reagent.
Contaminated soils and the reagent are mixed and heated in a treatment vessel. In the APEG
process, the reaction causes the polyethylene glycol to replace halogen molecules and
render the compound nonhazardous or less toxic. The reagent (APEG) dehalogenates the
pollutant to form a glycol ether and/or a hydroxylated compound and an alkali metal salt,
which are water-soluble byproducts. Dehalogenation (APEG/KPEG) is generally considered a
stand alone technology; however, it can be used in combination with other technologies.
Treatment of the wastewater generated by the process may include chemical oxidation,
biodegradation, carbon adsorption, or precipitation.

Dehalogenation is normally a short- to medium-term process. The contaminant is
partially decomposed rather than being transferred to another medium.

Synonyms:

DSERTS Code: N14 (Dehalogenation).

Applicability:

The target contaminant groups for dehalogenation treatment are halogenated
SVOCs and pesticides. APEG dehalogenation is one of the few processes available other than
incineration that has been successfully field tested in treating PCBs.The technology can
be used but may be less effective against selected halogenated VOCs. The technology is
amenable to small-scale applications. The BCD can be also used to treat halogenated VOCs
but will generally be more expensive than other alternative technologies.

Limitations:

Factors that may limit the applicability and effectiveness of the process
include:

High clay and moisture content will increase treatment costs.

The APEG/KPEG technology is generally not cost-effective for large waste volumes.

Concentrations of chlorinated organics greater than 5% require large volumes of reagent.

With the BCD process, capture and treatment of residuals (volatilized contaminants
captured, dust, and other condensates) may be difficult, especially when the soil contains
high levels of fines and moisture.

Data Needs:

A detailed discussion of these data elements is provided in Subsection 2.2.1 (Data Requirements for Soil, Sediment,
and Sludge). Treatability tests should be conducted to identify parameters such as water,
alkaline metals, and humus content in the soils; the presence of multiple phases; and
total organic halides that could affect processing time and cost.

Performance Data:

NFESC and EPA have been jointly developing the BCD process since 1990.
Data from the Koppers Superfund site in North Carolina are inconclusive regarding
technology performance because of analytical difficulties. There have been no commercial
applications of this technology to date. The BCD process has received approval by EPA's
Office of Toxic Substances under the Toxic Substances Control Act for PCB treatment.
Complete design information is available from NFESC, formerly NCEL and NEESA.
Predeployment testing was completed at Naval Communications Station Stockton in November
1991. The research, development, testing, and evaluation stages were planned for Guam
during the first two quarters of FY93. A successful test run with 15 tons of PCB soil was
conducted in February 1994.

Glycolate process has been used to successfully treat
contaminant concentrations of PCBs from less than 2 ppm to reportedly as high as 45,000
ppm. This technology has received approval from the EPA's Office of Toxic Substances under
the Toxic Substances Control Act for PCB treatment.

The APEG process has been selected for cleanup of PCB-contaminated soils at three
Superfund sites: Wide Beach in Erie County, New York (September 1985); Re-Solve in
Massachusetts (September 1987); and Sol Lynn in Texas (March 1988).

This technology uses standard equipment. The reaction vessel must be equipped to mix
and heat the soil and reagents. A detailed engineering design for a continuous feed,
full-scale PCB treatment system for use in Guam is currently being completed. It is
estimated that a full-scale system can be fabricated and placed in operation in 6 to 12
months.

The concentrations of PCBs that have been treated are reported to be as high as 45,000
ppm. Concentrations were reduced to less than 2 ppm per individual PCB congener. PCDDs and
PCDFs have been treated to nondetectable levels at part per trillion sensitivity. The
process has successfully destroyed PCDDs and PCDFs contained in contaminated
pentachlorophenol oil. For a contaminated activated carbon matrix, direct treatment was
less effective, and the reduction of PCDDs/PCDFs to concentrations less than 1 ppb was
better achieved by first extracting the carbon matrix with a solvent and then treating the
extract.

Cost:

The cost for full-scale operation is estimated to be in a range of $220 to
$550 per metric ton ($200 to $500 per ton) and does not include excavation, refilling,
residue disposal, or analytical costs. Factors such as high clay or moisture content may
raise the treatment cost slightly.

Additional cost information can be found
in the Hazardous, Toxic, and Radioactive Wastes (HTRW) Historical Cost Analysis System
(HCAS) developed by Environmental Historical Cost Committee of Interagency Cost Estimation
Group.

A
list of vendors offering Ex Situ Physical/Chemical Soil Treatment is
available from EPA
REACH IT which combines information from three established EPA databases,
the Vendor Information System for Innovative Treatment Technologies (VISITT),
the Vendor Field Analytical and Characterization Technologies System (Vendor
FACTS), and the Innovative Treatment Technologies (ITT), to give users access to
comprehensive information about treatment and characterization technologies and
their applications.